Antrim sewer plant upgrade in the works

By Shawn Hardy

Thursday

Feb 15, 2018 at 9:15 AM

Antrim Township supervisors received an update Tuesday night on plans to improve the treatment processes at the aging sewer plant with an eye to the nitrate removal requirements associated with cleaning up the Chesapeake Bay.

The two-phase project is under the control of the Antrim Township Municipal Authority, which owns the plant that is run by the township. Financing for the work, which will cost more than $9 million has not yet been discussed, according to Roger Nowell, the township's public works director.

The sewer treatment plant off Worleytown Road was constructed in 1978, with a major upgrade in 1998 so most of the equipment is 20 years old. A biosolids watering upgrade was done in 2015.

The first phase of the project involves the UV disinfection system, which does not have performance issues, but is at extreme risk of failure, which could result in non-compliance with the discharge permit, according to Scott Crosswell of GHD/CET Engineering. Because the system is so old, it would be hard to get repair parts if there were a breakdown.

A new UV system is being designed and could go out for bids late this month. Most of Crosswell's presentation was on the second phase of the project, so he did not have costs for the first phase readily available, but estimated it will be around $1.5 million.

Phase I construction could get under way in May, with the UV system in operation by December.

Phase II involves the sludge treatment process to remove nitrates. Nitrate removal is a key part of cleaning up the Chesapeake Bay and numerous municipalities have had to do plant upgrades as a result.

The Antrim plant has a cap of 21,918 pounds per year and discharge has been around 20,750 pounds per year for the last six years, according to Crosswell.

Credits had to be purchased in 2011 and 2016 when the cap was exceeded, which can happen when there are higher flows and colder weather. The biomass — comprised of the organisms that break down the waste — doesn't work as well when it is cold.

"The mechanical equipment is operating well with normal maintenance. The process is at its design capacity to meet the annual cap load for TN and there is a potential that the ATMA would have to purchase TN credits each year to meet the NPDES (National Pollutant Discharge Elimination System) cap load limits," according to the engineering report.

Three nutrient removal systems were evaluated: one calling for the addition of two tanks for a total of four; one with the addition of one larger tank; and an emerging technology known as ballasted activated sludge system (BioMag) in the two existing tanks.

The four-tank system is recommended because it remains operationally similar to the existing plant and "provides the most redundancy — with one tank offline, 75 percent of the treatment capacity is still available."

Total costs including construction and engineering are projected at $7,866,000. In addition, the facility will probably require a second operator and the report advises budgeting $75,000 annually for the position. Nowell said he plans to ask ATMA on Feb. 26 to move forward with engineering design for phase II, which could take about a year. With a construction period of 18 to 20 months, phase II would be operational in spring 2021.

Both phases are treatment improvements, but will not increase the capacity of the plant. The plant is designed to handle 1.2 million gallons a day and the average daily flow is a little over half of that at 0.697 million gallons per day.

Supervisor Fred Young wondered what would happen if a big commercial or industrial user was added to the system.

"Are there any Fresh Expresses coming down the road?" Young asked, referring to the salad processor.

"At the present location, I don't know what we could do to increase capacity," Nowell said, noting he recently had an inquiry from a current user about contributing 60,000 gallons more a day.

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